The invention relates generally to bearings that provide support to a flexible fluid-carrying umbilicus when coupled for use to a rotating fluid processing chamber. The invention also relates generally to centrifugal blood processing systems and apparatus that impart a twisting motion to an umbilicus to rotate a blood processing chamber.
Various blood processing systems now make it possible to collect particular blood constituents, rather than whole blood, from donors. Typically, in such systems, whole blood is drawn from a donor, the particular blood component or constituent is removed and collected, and the remaining blood constituents are returned to the donor. By thus removing only particular constituents, less time is needed for the donor""s body to return to normal, and donations can be made at more frequent intervals than when whole blood is collected. This increases the overall supply of blood constituents, such as plasma and platelets, made available for health care.
Whole blood is typically separated into its constituents through centrifugation. This requires that the whole blood be passed through a centrifuge after it is withdrawn from, and before it is returned to, the donor. To avoid contamination and possible infection of the donor, the blood is preferably contained within a sealed, sterile system during the entire centrifugation process. Typical blood processing systems thus include a permanent, reusable centrifuge assembly containing the hardware that spins and pumps the blood, and a disposable, sealed and sterile fluid processing assembly that actually makes contact with the donor""s blood. The centrifuge assembly engages and spins the fluid processing assembly during a collection procedure. The blood, however, makes actual contact only with the fluid processing assembly, which is used only once and then discarded.
To avoid the need for rotating seals, and to preserve the sterile and sealed integrity of the fluid processing assembly, blood processing systems often utilize centrifuges that operate on the xe2x80x9cone-omega, two-omegaxe2x80x9d operating principle. This principle, which is disclosed in detail in Brown et al., U.S. Pat. No. 4,120,449, enables centrifuges to spin a closed system without the need for rotating seals and without twisting the components of the system. Blood processing systems that make use of the principle typically include a fluid processing assembly that includes a plastic bag that is spun in the centrifuge and that is connected to the blood donor through an umbilicus. The umbilicus is turned back on itself in the form of an inverted question mark, so that an end portion of the umbilicus is coaxially aligned with the axis of rotation of the bag. The intermediate portion of the umbilicus is twisted as the bag is spun to counteract the twisting that would otherwise take place as the bag is spun. The effect is that the end of the umbilicus, which is opposite the bag and is connected to the donor, does not twist as the bag is spun. The sealed, sterile integrity of the fluid processing assembly is thus maintained without the need for rotating seals.
U.S. Pat. No. 5,551,942 to Brown et al., commonly owned by the assignee hereof, discloses one such blood processing apparatus based on the xe2x80x9cone-omega, two-omegaxe2x80x9d operating principle. In this apparatus, a disposable fluid processing assembly having an umbilicus and a processing chamber is mountable within a centrifuge assembly. One end of the umbilicus is held rotationally stationary substantially over the axis of centrifugation. The other end of the umbilicus joins the processing chamber and rotates with the processing chamber around the axis of centrifugation at the two-omega speed. The mid-portion of the umbilicus is supported by a wing plate that rotates around the axis of centrifugation at the one-omega speed. A bearing mounted on the umbilicus permits the umbilicus to rotate relative to the wing plate as the wing plate and the processing chamber turn at different speeds. The bearing slides into a one piece gimbal mounted in a recess provided on the wing plate. The gimbal helps keep the fluid processing assembly properly positioned during the centrifugation procedure. When the procedure is completed, the bearing can be slid out of the gimbal in the wing plate to permit removal of the fluid processing assembly.
One aspect of the invention provides a bearing for supporting a rotating element. The bearing possesses enhanced flexural modulus, heat resistance and resistance to deformation during use.
In one embodiment, the bearing comprises an inner annular body and an outer annular body about the inner annular body. A bearing surface, which is located between the inner annular body and the outer annular body, supports the outer annular body for rotation about the inner annular body. A cage supports the bearing surface during rotation of the outer annular body about the inner annular body. The cage includes a material that imparts increased flexural modulus that resists deformation during rotation.
Another aspect of the invention provides an umbilicus for use in association with a fluid processing system. The umbilicus comprises an umbilicus body, which carries the bearing.
Another aspect of the invention provides a fluid processing system, e.g., for blood, which includes a fluid processing chamber that, in use, rotates about an axis. An umbilicus carrying the bearing is coupled to the fluid processing chamber by a bearing support. The bearing support is rotated to impart a twisting motion to the umbilicus, to thereby rotate the fluid processing chamber about an axis.
Features and advantages of the invention are set forth in the following Description and Drawings, as well as in the appended claims.